The use of synthetic polymers in drug delivery devices has focused on "smart polymers" a term ascribed to polymers which form gels that have the ability to expand or contract in response to a specific stimulus, such as light, temperature or pH. Typically, such polymers will precipitate in solution or collapse with concomitant expulsion of gel pore contents. In some cases, these processes are reversible.
Synthetic polymers may be based on a number of types of monomeric units, including vinyl monomers, N-alkyl substituted acrylamides and the like. Copolymers have also been utilized in an attempt to combine or modulate the stimulus responsive properties of one or more known smart polymers.